1. Field of the Invention
This invention relates to catalysis. In one aspect, the invention relates to the catalytic oxidation of an aldehyde to the corresponding carboxylic acid while in another aspect, the invention relates to the use in this oxidation of a promoted, phosphomolybdic oxide catalyst.
2. Description of the Prior Art
Various methods are known for converting aldehydes to carboxylic acids, particularly acetaldehyde to acetic acid. For example, Thomas et al., U.S. Pat. No. 1,985,750, teach the oxidation of acetaldehyde to acetic acid in the presence of manganic salts, particularly manganic acetate. Whitfield and Kemp, U.S. Pat. No. 3,103,535, teach the production of aliphatic carboxylic acids by contacting an aldehyde with a gas containing free oxygen in the presence of one or more metals of variable valency and phosphate ions. Sennewald et al., U.S. Pat. No. 3,655,747, also teach the production of carboxylic acids by the oxidation of aliphatic aldehydes with oxygen but in the presence of a carrier catalyst containing metallic palladium and/or palladium oxide and/or a palladium salt and at least one other metal, such as platinum, rhodium, ruthenium, etc. Other processes are known and some of these involve sensitive intermediates, such as a method currently in industrial use for preparing acetic acid which utilizes a peroxy acetic acid intermediate a compound with considerable explosive potential. Still other methods are known, including those taught by Hull, U.S. Pat. No. 2,578,306 and Schaum et al., U.S. Pat. No. 4,094,901.